My notes

The native file format of Inkscape is the plain-text standard
SVG format.
The file can be edited with a text editor. Inkscape also includes
an XML editor, in the Edit menu. It is sometimes
convenient for making changes that might be awkward using the GUI.

Some Web browsers, including Firefox, can display SVG directly.
For further information, see

For the graphics to scale nicely to the requested size,
make sure that the root svg element in
the .svg file contains a
viewBox attribute.
Inkscape does not normally create a viewBox
attribute, but one can be added using the built-in XML editor.
(See Bah's
Positioning SVG.)

An SVG drawing can be used as a link inside an
a element by using <img>
rather than <object>
(see Bah's
The <img> Tag).
It is also possible to define links within the SVG itself.

There is a
bug
in Inkscape 0.47 and 0.48 that can cause an open path to become
closed when exported to PDF, PS or EPS if the path endpoints are
aligned. A work-around is to offset one of the endpoints slightly.
The bug is actually in Cairo and has apparently been fixed
in at least Cairo 1.12.2.

To be able to import EPS files, see
What formats can Inkscape import/export?.
Importing EPS files has sometimes resulted in problems. The method that
Inkscape uses is defined by eps_input.inx in
/usr/share/inkscape/extensions/
(c:\Program Files (x86)\Inkscape\share\extensions\ on my Windows 7 machine)
or ~/.inkscape/extensions/. At various times it has used
different converters: gs, pstoedit, ps2pdf. If problems occur, a workaround
may be to just manually use one of these converters to produce a
.svg file. We recently (2012 Aug 7) had good luck with pstoedit.

UniConvertor can be used by itself or from within Inkscape to
permit the reading of CorelDraw files. Once Inkscape 0.47+ and
UniConvertor 1.1.5 have been installed, running UniConvertor's
‘Inkscape patch script’ integrates the two.
As of version 1.1.5, UniConvertor still doesn't import text
from the CorelDraw file.

To make arrow heads (and other line markers) the same colour as their
line, select the line and use
Extensions ▶ Modify Path ▶
Color Markers to Match Stroke.

Regions with shared boundaries:
Neither Inkscape nor the SVG specification itself supports regions with
shared boundaries (see thread from 2013 May).
A partial work-around (thanks to Alejandro Castillo for the clue)
is to create two copies of the shared
boundary and then edit the nodes on both copies at the same time.
For example, to create the image on the right I did the following:

Create paths A, B and C, using Snap to
cusp nodes to get the nodes where they touch to match
exactly.

Use Edit ▶ Copy and
Edit ▶ Paste In Place to make
path D as a copy of path C.

Combine paths A and C into a closed path, and paths B and D
into a closed path, so fills can be specified.

To move a node on the shared boundary, simultaneously
select both path A+C and path B+D, then use
rubber-band selection to select the desired node
in both path C and path D. There's a bug that causes the
selected nodes to disappear, but they're still there and selected.
The nodes can be moved using either the mouse or the keyboard.
It doesn't seem to be possible to move their handles using the
mouse; the keystrokes to
Scale handle
do not work for me (Inkscape 0.48) but the keystrokes to
Rotate handle
do work.